1. Field of the Invention
The present invention relates to a semiconductor device in which a high speed and high integrated compound semiconductor element such as gallium arsenide is used, particularly relates to a semiconductor device which is used in a high speed signal processing, and also relates to a method for producing such a semiconductor device.
2. Description of the Prior Art
In many cases, there has been used a gallium arsenide semiconductor device for performing a high speed signal processing in a high frequency band, particularly in a GHz band and higher frequency band.
FIG. 1 shows an example of a conventional packaging type of a semiconductor device in which gallium arsenide is used as a semiconductor element.
FIG. 1(a) is a sectional view showing an example of a constitution of a conventional gallium arsenide semiconductor device. As shown in FIG. 1(a), there is disposed a semiconductor chip 3 made of gallium arsenide in a concave portion 2 provided in the central portion of a base 1 made of ceramics such as alumina, and electrodes (not shown) of the gallium arsenide chip 3 are connected to terminals of a thick film printed circuit 4 formed on the peripheral portion of the concave portion 2 on the base 1 through bonding wires 5 made of such as aurum material.
However, the surface of the ceramic base 1 is so uneven that it is difficult to form a circuit with high precision thereon. Therefore, the minimum width of a thick film printed circuit 4 is approximately 100 .mu.m, resulting in that it is impossible to package a circuit with high density. Particularly, since it is difficult to form a ground circuit for isolation, impedance conformity cannot be performed, so that the degree of freedom of the connecting circuit pattern is small.
FIG. 1(b) is a sectional view showing another example of packaging type of a conventional semiconductor device. As shown in FIG. 1(b), there is formed a thin film circuit 12 on the flat upper surface of a ceramic base 11, and the thin film circuit 12 is connected through wires 14 to a gallium arsenide semiconductor chip 13 which is disposed to be die-bonded in the central portion of the base 11. Even in this case, however, since the base 11 is made of ceramics, the minimum width of the thin film circuit 12 may be made only approximately 10 .mu.m so that an integral multi-pack film circuit can not be formed, resulting in that the conventional semiconductor device is not suitable to a package with high density.
FIG. 1(c) is a sectional view showing still more another example of a packaging type of a conventional semiconductor device. As shown in FIG. 1(c), in this case, there is disposed and die-bonded a gallium arsenide chip 23 in the central portion of the upper surface of a silicon substrate 21 having a thin film circuit layer 22 formed on the surface of the silicon substrate 21. The thin film circuit layer 22 is connected to the gallium arsenide chip 23 through wires 24. In this case, since the flatness of the surface of the silicon substrate 21 is remarkably improved because of adopting a silicon substrate, the minimum width of the thin film circuit layer may be made approximately 3 .mu.m.
However, in any case mentioned above, since wires are used for connecting between the gallium arsenide chip and the thin film circuit, there is a limitation thereby so that the sufficient high density of the thin film circuit has not yet accomplished. Moreover, since the wiring device has a circuit capacity, there often occurs a time lag, so that the conventional semiconductor devices as mentioned above are not suitable to high speed operation.